steam injection - cairo university...injection pressure (psia) water cut (%) 32 25/12/2017 dr.helmy...

1

Steam Injection

Dr. Helmy Sayyouh

Petroleum Engineering

Cairo University

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Increasing Temperature Lowers Viscosity...

Fig. 11-1

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Single-Parameter Viscosity Correlation

Fig. 11-5

Two-parameter correlation

2 AeB/T

Andrade equation

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Thermal Properties of Water

Table 11-2

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Pressure-Specific Volume of Water

Fig. 11-4

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Enthalpy of Water...

Fig. 11-3

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Thermal Properties of Selected Rocks

Table 11-3

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Graphical Construction of Hot Water Flood

Fig. 11-6

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How Heat is Lost...

Heat management is the single most

important factor in the commercial success

of thermal recovery projects

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Heat Loss Sources...

Surface equipment

Rock and water in formation

From wellbore

To adjacent strata

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Water Issues...

Requires fresh water source (not produced water)

Scaling in surface boiler…

Chemical treatments

Restricted to 80% quality steam

Intensive surface purification needed

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Losses to Rock and Water

Usually the largest source of loss

Avoid low porosity formations (f>0.3)

Avoid high water saturation

Sof >0.3

Use steam, not hot water

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Schematic Temperature Profile in Drill Hole

Fig. 11-7

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Wellbore Heat Loss

Fig. 11-11 Fig. 11-12

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Controlling Wellbore Loses...

Inject as fast as possible

Consider downhole generators

Evacuate annulus

Insulate tubing…. Steam depths

<1500 ft. for uninstalled tubing

<7000 ft. for insulated tubing

In situ combustion (high pressure air injection)

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Thermal Methods

Process variations

Physical properties

Fractional flow in thermal floods

Heat losses from wellbores

Heat losses to over/underburden

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Losses to Adjacent Strata...

Fig. 11-13

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Thin Reservoirs Lose Heat

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Effect of Oil Saturation, Reservoir Thickness, and

Net/Gross Ratio

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Ways to Control Heat Loss...

Restrict application

Avoid deep reservoirs

Avoid low porosity reservoirs

Isolate injection string

Insulate tubing

Evacuate annulus

Operational considerations

Inject at large rate

Reduce rate after breakthrough

25/12/2017 Dr.Helmy Sayyouh21

Steam Quality Drop in Steam Pipelines

If the steam quality at the generator is

Xgen, fraction, then the wellhead steam

quality is given by

Xwh = Xgen - Q.L/M. Lv

Where:

Q = heat loss rate, Btu/hr-ft

L = pipe length, ft

M = mass flow rate of steam, lb/hr

Lv = enthalpy of vaporization, Btu/lb


Steam Quality Drop in the Wellbore

Given the wellhead steam quality, Xwh,

the formation face steam quality is given

by

Xsf = Xwh - Q L/ M Lv

Where, L is casing/tubing length.


Thermal Stress in Casing

Wellbore heat loss leads to an increase in the casing temperature, and the thermal stress is given by

S = ά E (Tc-Tf)

Where ά is the coefficient of expansion for steel and E is Young’s modulus for steel.

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Zones in a Steam Drive...

Fig. 11-18

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Midway Sunset Response

From Jones (2007)

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Kern River 10 Pattern Flood (Chevron)

Depth, ft 700- 770

Oil gravity, oAPI 14

Original reservoir pressure, psi 225

Current reservoir pressure, psi 60

Average net sand thickness, ft 70

Oil viscosity at 85 oF, cp 2,710

Oil viscosity at 350 oF, cp 4

Average permeability, md 7,600

Average porosity, percent 35

Average oil saturation, percent 52

Residual oil saturation, percent 33

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Kern River 10 Pattern

In seven yr test

18.6 MM bbls steam inj

3 MM bbls oil recovered

Cum OSR = 0.16

SOR ~ 6.15

37% oil recovery

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Ten-Pattern Performance Well...

Table 11-5

1/OSR

Cumulative

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Gravity Override...Kern River

Fig. 11-23 Fig. 11-24

Overburden

Underburden

T

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Duri Field, Phase 1

Process type: Steamdrive

Location: Sumatra, Indonesia

Operator: P.T. Caltex Pacific Indonesia

Lithology: Sandstone

Subsurface depth: 150-240 m

Oil viscosity: 157 mPa-s

Pressure: 750 kPa

Sq. km/producer: 0.05

Water salinity: 900 - 4500 ppm NaCl

Est. % IOR: na

1370 steam injectors, 3810 producers

Oil prod. = 204x103 B/D

Steam inj. = 730x103 B/D

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Duri Field, Phase 1

From Enhanced Oil Recovery Field Reports, SPE

10

100

1000

10000

100000

1000000

1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992

Oil Rate (BOPD)

Injection Rate (BCWEPD)

Injection Pressure (psia)

Water Cut (%)


Advantages and Limitations

Steam flooding has emerged as the major thermal

recovery process because of its relative low front-end

cost, ease of steam generation on site, low operating

cost, and proven success


However, it may suffers from the following limitations:

Lack of availability of large quantities of high quality fresh water.

Completion of producers with equipment to accommodate high temperature fluctuations creates many problems.

Reservoirs should be shallower than 5,000 ft.


Reservoir rocks should not contain fresh water-

sensitive clays.

Emulsification and sand production may be

encountered.

25/12/2017 Dr.Helmy Sayyouh 35

Steam Cycling Process

Injection Phase:

High quality steam is

injected into a producer.

Injection is achieved at the

highest practical injection

rate, to minimize heat

loss.


Soaking Phase:

Well is shut-in for some time allowing steam to heat the region.

Optimum soaking duration is programmed to achieve a balance between maximizing the heated volume around the well and minimizing the loss of heat to the formations above and below.


Production Phase:

producer is put back on

production until the oil

rate declines to the

economic limit.

The above cycle is repeated

(two to three times, in

general) until oil rate

response becomes

uneconomical.


Cycling steam stimulation is one oil recovery

method which is known to be effective in

recovering oil from heavy oil reservoirs.

The field use of this technique dates back to

1958, when Shell Oil Company steamed a

well of the Yorba Linda oilfield of California.


Cyclic steam stimulation process is widely

used in Canada and Venezuela because of

its applicability in very viscous oil

formations, and quick payout.


The total oil recovery by steam

stimulation averages about 10 to

15% of the oil-in-place.

In Cold Lake, Alberta, it is over

25% or higher.


In Venezuela, cycling steaming is a

well established procedure for

recovering heavy oil and recoveries

from this process as high as 40%

have been noted.


Advantages and Limitations

Well Stimulation by Huff-&-Puff is a widely

process because of its relative low front-end

cost, ease of steam generation, low operating

cost, quick pay-out, and proven success.

Well stimulation is now a commonly used

method to prepare wells for inter-well steam

flood projects.


Wells designed as steam injectors provide

current income from the oil produced. And,

subsequent oil injectivity is improved.

Wells designated as oil producers provide

higher current income. And, subsequent oil

productivity is improved.


Design Criteria

Typical design criteria for finding out whether

an oil reservoir is a good candidate for steam

injection were established:


Formation depth may be above 200-400 ft

(200 ft in Charco Redondo, Texas) to

avoid parting pressure of adjacent

formations and should be limited to 5000

ft ( Brea, California) due to heat loss.

Higher limit possible using downhole

generators.


To minimize heat loss, formation thickness should be not less than 30 ft (Slocum, Texas).

Formation permeability should be high (between 250 and 1000 md) and porosity should be higher than 18 to 20 %( Shiells, California).

The oil gravity should be in the 12-25 API range with viscosity about 2000 cp at reservoir temperature.


The upper limit can be decreased to 4000 cp or less by cyclic steam injection.

Steam injection is applied also to light oils (Brea, California, with 24ºAPI and 6 cp and El Dorado, Kansas, with 37º API and 4 cp).

Oil saturation at the start of steam injection project should be higher than 40 to 50%.


The injection should be as rapid as possible.

Shallow and dip oil reservoirs, thick pay zones with very good permeability, cheap and high quality water source are some favoring factors to steam injection, while strong nonuniformity, highly water-sensitive clay content, and low interwell communication are adverse factors.


Properties of Tar Reservoirs at locations tested by steam injection

Steam Drive Steam SoakDepth, ft 935 – 3800 269 – 2500

Net Thickness, ft 110 – 210 52 -110

Gravity, ºAPI 5 – 9.3 2 - 9

Temperature, ºF 52 – 140 55 – 110

Oil Viscosity, cp 2,159 – 1.6 Million 25,000 – 20 Million

steam injection - cairo university...injection pressure (psia) water cut (%) 32 25/12/2017 dr.helmy...

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